J. mar. biol. Ass. India, 1975, 17 (1) : INTERTIDAL ECOLOGY OF THE SEA SHORE NEA^ TARAPUR ATOMIC POWER STATION*

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1 J. mar. biol. Ass. India, 1975, 17 (1) : INTERTIDAL ECOLOGY OF THE SEA SHORE NEA^ TARAPUR ATOMIC POWER STATION* M. C. BALANI Health Physics Division, Bhabha Atomic Research pentre, Bombay- 85 ABSTRACT Surveys were carried out between March 1969 and August 1970 to study the fauna and flora in the littoral zone of the sea shore near the Tarapur I Atomic Power Station. The beach adjacent to the station is rocky with a number o tidal pools inhabited by a variety of organisms whereas the beach to the south is mo tly sandy and barren except for a small rocky stretch. The tidal range is 6 m and{ over a mile of beach is exposed during low tide. The near shore currents are v^ry strong and have a clear north-south oscillation with the changing tides. Less Atherina sp. fry were available near the Power Station in March 1970 than during the previous year. Possible reasons for these differences pre discussed, including the effect of heated discharges on biota. The need is also emphasiied to monitor the biota (Plankton, Nekton and Benthos) systematically for content of fissipn products released by the Power Station. ' INTRODUCTION THE Tarapur Atomic Power Station (TAPS) is situated oh a rocky promontory, south of the Tarapur light house located about 100 kms n rth of Bombay (Fig. 1). The sea adjacent to the Power Station receives heated efflueits as well as low radioactive wastes from the Power Station. Intertidal comrjiunities are known to play a significant role in the cycling of radionucudes in the marine ecosystem. Moreover some organisms of the intertidal community ike oysters and clams which are consumed by the local fisherfolk are well ki lown concentrators of radionuclides like Mn^* and Zn^^ (Qupman et al., 1958; l^air et a/., 1969) constituting thereby a health hazard to the local population The present paper reports results of periodical ecologidal surveys of the 6 kms stretch of sea shore near the TAPS extending from Uchhepi creek in the south to Tarapur light house on the north. Thanks are due to Dr. A. K. Ganguly, Head, Health Fjhysics Division, Bhabha Atomic Research Centre, for his kind encouragement and! to Shri K. V. K. Nair for going through the manuscript and helpful criticism. lassistance rendered by S/Shri G. R. Doshi and CD. Mulay in the field collection s duly acknowledged. TOPOGRAPHY OF THE AREA Cartwright and Spanne (1964), have studied the maj )r features in the topography of the area. They have assigned an arbitrary elefvation of 100 feet to a *Presented at the 'Symposium on Indian Ocean and Adjacent ias Their Origin, Science and Resources' held by the Marine Biological Association of India a{ Cochin from January 12 to 18, [1]

2 102 M- C. BALANI beach mark on the plinth of the Tarapur light house (Fig. 2). Landward of the 100 feet contour the slopes range from 1 to 2% and the surface material consists of sand with occassional outcroppings of rocks. Seaward of the 100 feet contour upto 92 feet contour the slopes range from 4-6%. The slope of the foreshore segment between 92 and 76 feet contour is 1 % and is marked by numerous pools and depressions formed by natural and man made barriers and the area is made up of basaltic rocks and breccia. Seaward of the 76 feet contour for a distance of about 1,500 feet (3 fathom line) the average slope is again 1 % and the bottom is irregular in this stretch. N -*t LIGHT HOUSE, d. 10 Fig. 1. Site map showing the Power Station and the near by sea environment. DESCRIPTION OF THE BEACH The sea shore from Tarapur light house to 2 kms south of the Power Station is rocky, the rock principally of the basaltic type. The rocky shore shows no evidence of any accretion of sand or silt. To the south of this is the sandy beach (3 kms) extending upto Uchheli creek. To the north and south of the Power Station, over [2]

3 INTERTIDAL ECOLOGY NEAR TARAPUR ATOMIC PCVER STATION 103 a mile of the shore (intertidal area) is exposed during a sprini lowtide. This stretch of the shore is interspersed with several tide pools. ThI shore narrows down further south at the confluence of the rocky and sandy shores. The sandy shore upto Uchheli creek is about 1 km wide. It is wider at bqth the extremities and narrows down in the middle. \.1 > V> '3. Fig. 2. Intake and discharge Canal System of the Powejr Station. HYDROGRAPHIC CHARACTERISTICS OF THE NEARSHPRE WATERS The sea adjacent to the Tarayur Coast is very shallowf and is characterised by large tidal differences, about 6 m for spring tides (Car wright and Spanne, loc. cit.). Associated with the tides are strong north-south tidal currents which reverse directions every six hours. A hydrobiological survey (ifjair, 1968) conducted [3]

4 104 M. C. BALANI during March and October 1966 showed salinities ranging from to %o in March and %o to % in October. Sea surface temperatures ranged from 27.3 C in March to 31.5 C in October. Temperature measurements were carried out along the intake and discharge canal systems (Fig. 2) during December The discharged water at its point of release from the reactor had a temperature 5.5 C higher than the intake water. The Rocky Shore The rocky intertidal area at Tarapur can be divided into an upper littoral, mid-littoral and sub-littoral zones. The upper littoral is that area covered by the 100 and 92 feet contours, mid-littoral is that covered by 92 and 76 feet contours and sub-uttoral, seaward of the 76 feet contour upto the 3 fathom line. Upper Littoral The upper littoral region remains practically dry except during high water springs when it gets covered. This area abounds in an Anomuran crab Eupagurus sp. The density of population of this species was found to be as much as 28/sq. feet and they seem to breed in the month of December. Other less common inhabitants of this region included crabs like Carybdis orientalis, Dotilla myctiroides, Leptodius sp. and Grapsus striagasus. Gastropods were represented by Finella Cerithinia and Nerita oryzarum in fair abundance respectively during the months December and July. Other gastropods recorded from this zone included Astria stellata, Euchelus indicus and Bursa tuberculata. Mid Littoral The mid-littoral zone remains exposed during low tide but gets covered invariably during high tides. The cirripede crustacean Balanus amphitrite is the most abundant inhabitant of this zone (density of population /sq foot), although most of them were found dead during the month of December. Among gastropods Cellana radiatia was the most common. Other less common gastropods included Onchidium veraculatum and chiton sp. Tide Pools The receding high tide leaves behind several tide pools. The tide pools harbour a variety of forms. Coelenterates were represented by coral Favia sp. and sea anemones. Among errant polychaetes Perinereis sp. was recorded. Acetes indicus a macruran decapod was also common during March Among the fishes recorded were Gobiids Periophthalmus sp. Atherina sp. (Teleostei) fry were in abundance during March 1969 and were less common when the area was revisited in March 1970, possibly due to the higher temperatures of warm water discharges from the reactors. Among the seaweeds (chlorophyceae) recorded were Caulerpa sertularoides abundantly encrusted with carbonate of hme, Derbesia sp.. Viva lactuca and Enteromorpha intestinalis. Rhodophyceae were represented by Gracilaria sp. which were found attached to the rocky bottom. [4]

5 INTERTIDAL ECOLOGY NEAR TARAPUR ATOMIC Poi^ER STATION 105 Sub-Littoral f The sub-littoral region is covered throughout the year. The bottom is hard and coralune with attached algae, Sargassum sp. (Phaeophyfceae). The dominant coral found in this zone is Favia sp. t SEASONAL DISAPPEARANCE OF FAUNA AND j FLORA A survey during the monsoon months indicated total! absence of seaweeds and most of the dominant fauna possibly due to the salinityf changes during monsoon, however, gastropods Cellana radiata and Onchidium vendfulatum were available in abundance on the rocks of mid littoral region. Upper littpral region had Nerita oryzarum in abundance during this period. ZONATION Although the distribution of fauna is over the entire ro^ ky stretch some semblance of a zonation is noticeable. In the upper littoral Eupagurus species are evenly distributed and this zone can be described as the.lupagurus zone. The mid-httoral has an upper Balanoid zone and a lower zone lominated by Cellana radiata. The rocky intertidal surface generally provides a firm substratum for many an intertidal community to thrive well. But the intertidal surmces near Tarapur in general seem to have much less density of fauna compared t, other similar shores on the west coast of India. This could possibly be due to tile constant reworking of the shore for site development purposes for the Power Station during the past four years. Sandy shore I The sandy shore is in many ways less favourable to life thin the rocky intertidal surface, yet some organisms have been remarkably successful in colonising it. Analogous to the rocky shore the sandy shore also can be classified j into upper, mid, and sub-littoral zones. 5 I Anomuran crab Gelasimus marionis is found distributed widely in the upper littoral region. A tube dwelling polychaete, Eunice sp. was also recorded from this zone, although its regular occurrence appears rather dpubtful. The mid-httoral zone abounds in the tube dwelling polychaete Eunice sp. although rare gastropods Conus sp. and echinoderms represented by crinoids were also recorded. Sponges Adosia sp. was also found attached fp isolated projections on the sandy beach. SEAWEEDS WASHED ASHORE The seaweeds cast ashore included Codium sp. and [//vajsp. (Chlorophyceae), Dictyota sp. and Sargassum sp. (Phaeophyceae) and Spyridia Isp. (Rhodophyceae). ECOLOGY OF THE UCHHEU CREEK j The creek lies about 5 kms south of the reactor site and is cjf importance because of its oyster and clam fisheries. [5]

6 106 M. C. BALAN! Among the Pelecypods, clams like Meretrix meretrix, M. Costa and Katelysia opima were found in abundance in the upper reaches of the creek. Onchidium verraculatumvias a. common gastropod found on the rocky shore line of the creek. Aplysia benedicti was recorded during March and their eggs in the form of long strings attached to the stones and seaweeds were obtained in the month of December possibly indicative of their breeding season. Two species of oysters, Ostrea, gryphoides and Ostrea crenulifera constitute the oyster fisheries, the most important fishery in the creek. These oysters and clams are significant concentrators of induced radionuclides like Mn^* and Zn^s and would serve as useful indicators for build up of induced Mn6* and Zn^^ radioactivity in the shore waters at Tarapur (Kamath et al., 1966). Similarly P '^ is accumulated in soft tissues of fishes. I''* by fish and phaeophyceae. Fe^^ is accumulated by plankton, Sr^ by brown algae in preference to Ca and Co^o and Mn^* by marine Crustacea. The ability to accumulate radionuclides is related to the position of the particular organism in the intertidal zone as well as in the food chain of the area. For instance Aplysia benedicti accumulates Co^o from the environment (Patel and Valanju, 1970) 10* times than that in the environment mainly through its food which consists of chlorophycean algae which are sub-littoral in habitat. REFERENCES CARTWRIGHT, P. AND G. A. SPANNE Tarapur Atomic Power Plant circulating water system, proposed double discharge system. Report to Government of India (Restricted). Atomic Power equipment Department, General Electric, San Jose, California. CHIPMAN, W. A., T. R. RICE AND T. J. PRICE Uptake and accumulation of radioactive zinc by marine plankton, fish, and shellfish. Fish. Bull., 135: U.S. Department of Interior, fish and wildhge service. KAMATH, P. R., I. S. BHAT, A. A. KHAN AND A. K. GANGULY Preoperational search for baseline radioactivity, critical food and population group at the Tarapur Atomic Power Station site. Proc. First IRPA Congress. Pregamon Press, Oxford. NAIR, K. V. K Hydrobiological surveys off Tarapur. BARC/H.P/P.M/11. Bombay, India., Y. M. BHAT AND G. R. DOSHI Fallout radioactivity in three brackish water malluscs from Kerala. Curr. Sci., 38 (14): PATEL, B. AND P. G. VALANJU Radioecology of Aplysia benedicti (In Press). [6]